Lump Trivia ... Crusin' at 250

Jeepster47 · February 2016

I used a large nested egg with a KAB, Smokeware cap, and a Flame Boss 200 for control while collecting data. The ambient temp range was 20 ~ 40 degrees and the humidity was around 80% for all three tests. My cook area is sheltered on three sides so the egg was not subjected to high winds. Rockwood lump was weighted (to 0.1 oz) before and after each of three cooks ... ~1 hr, ~6 hrs, ~17 hrs ... the difference was used to plot the lump usage axis. For the time axis, hours at 250 degrees was used.

Here's a graph of the data with a best fit line for the nerds:

Image: https://us.v-cdn.net/5017260/uploads/editor/bc/kyy2pnxdhhll.jpg

If we round off some of the numbers from the best fit line, then we can conclude that it takes approximately 2/3 of a pound of lump to warm up the egg to 250 degrees and then shut it down. Once it's warmed up and is percolating along, it's burning approximately 1/3 of a pound of lump per hour.

If we assume that half the warm-up-cool-down lump is used to warm up the egg (1/3) pound, and there is 1-1/3 pounds left when the fire goes out (previous thread), we have 8-1/3 pounds left from a 10 pound (to the bottom of the notches) fill. That equates to a 25 hour cook at 250 degrees. Fill to the top of the fire ring and the cook time will drop to about 10 hours. Fill to the top of the KAB and the cook time will drop to about 4 hours!

One observation: Although the data suggests that you can cook for 25 hours on a 10 pound fill, you will be lucky to achieve that without an intervention at about the 15 hour point ... wiggle stick and leveling of the lump would be helpful.

buzd504 · February 2016

When you are weighing used lump, how do you distinguish between ash (unusable), fines (which still have burn potential), and partially burned lump (which may have potential to produce heat that isn't consistent with its weight, depending on how burned it is) ?

Jeepster47 · February 2016

@buzd504 ... I tried to take the data in a "this is how I cook" manner. Thus, I used the KAB to shake out the ash and any lump that would fall through the basket. I also used a KAB to weed out the fines and small pieces when loading the egg out of a fresh bag of lump. I would argue that the amount of energy in any fines or small burnt pieces is a small variable.

There are other variables affecting the consumption of BTUs more than fines. How much protein is on the grill? I had one rack of ribs for the 6 hr test and one pork butt for the 17 hr test. Had I cooked a half dozen of each, then the lump per hour value would have been higher and overshadowed the BTUs lost through the KAB.

Thanks for the question ...

chadpsualum · February 2016

This screams for 1 more test around 12hrs. Regardless, I love this kind of stuff. Good work!

Btw...did you start with the approx the same amount of lump each time?

Jeepster47 · February 2016

@chadpsualum ... the one hour cook was nominally 6 pounds, but the other two were nominally 10 pound cooks. They're nominal fills 'cuz I had to account for the smoke wood that was used. Converted the weight of smoke wood to BTUs and then converted the BTUs back to an equivalent amount of Rockwood lump. Turns out that adjusting the fill numbers didn't change the final numbers from the curve that much.

fishlessman · February 2016

theres also the factor of direct verse inderect, i did an overnight butt cook raised grid direct once and it burned very little lump. maybe 2/3 less

fishlessman · February 2016

always wondered how much more gets burned with a controller verse just doing it manually

Jeepster47 · February 2016

@fishlessman ... forgot to mention that variable. I used an AR rig with the oval stone, oval drip pan, and one grill.

Why do you think direct vs indirect affects lump usage?

chadpsualum · February 2016

Jeepster47 said:

@fishlessman ... forgot to mention that variable. I used an AR rig with the oval stone, oval drip pan, and one grill.

Why do you think direct vs indirect affects lump usage?

Heat retention of the platesetter?

Jeepster47 · February 2016

fishlessman said:

always wondered how much more gets burned with a controller verse just doing it manually

Got to laugh about that question. I though I had all the variables in hand before taking the first data point. Turned out that lump in an egg is a true Pandora's box. Every time I had one variable accounted for a couple more popped up to consider.

Your question is a good one ... that I don't know the answer to. If you set up the controller like @stlcharcoal does - where the controller comes on only once in awhile - then the answer is probably they are the same. If you set it up like I do - fan running around 20~30% of the time - then more air cool air is forced into the egg, is heated up to temp, and then vented to the outside. That would suggest that lump usage with the controller is higher ... but, how much?

Jeepster47 · February 2016

chadpsualum said:

Jeepster47 said:

@fishlessman ... forgot to mention that variable. I used an AR rig with the oval stone, oval drip pan, and one grill.

Why do you think direct vs indirect affects lump usage?

Heat retention of the platesetter?

Okay, but that's an extremely small about of BTUs to heat it up ... and once at temp, it should not require extra BTUs to keep it at temp. Yes/no?

fishlessman · February 2016

Jeepster47 said:

@fishlessman ... forgot to mention that variable. I used an AR rig with the oval stone, oval drip pan, and one grill.

Why do you think direct vs indirect affects lump usage?

it either does something to the heat flow or its reflecting the heat down into the pit, i did a large cook once with an oversized stone in the large once, had a dome of around 200 and looking down there was a 1000 degree inferno under the stone. ive also had some neat effects using a round bottom deflector where i could get the dome hotter than the stone, actually had a blue flame hovering in the dome over the stone, broiler effect. direct verse inderect, the direct wins out large, but you need to start with very little lump and raise the grid as high as possible. heres a visual
http://eggheadforum.com/discussion/507801/cooking-a-butt-direct

chadpsualum · February 2016

Jeepster47 said:

chadpsualum said:

Jeepster47 said:

@fishlessman ... forgot to mention that variable. I used an AR rig with the oval stone, oval drip pan, and one grill.

Why do you think direct vs indirect affects lump usage?

Heat retention of the platesetter?

Okay, but that's an extremely small about of BTUs to heat it up ... and once at temp, it should not require extra BTUs to keep it at temp. Yes/no?

I was just thinking of insulating effects...

Jeepster47 · February 2016

@fishlessman ... hard to argue with facts, isn't it! So, there's another escapee from Pandora's box.

Jeepster47 · February 2016

chadpsualum said:

I was just thinking of insulating effects...

Fishlessman's experience seems to support your position.

Jeepster47 · February 2016

chadpsualum said:

I was just thinking of insulating effects...

Fishlessman's experience seems to support your position.

Ragtop99 · February 2016

Jeepster47 said:

fishlessman said:

always wondered how much more gets burned with a controller verse just doing it manually

Got to laugh about that question. I though I had all the variables in hand before taking the first data point. Turned out that lump in an egg is a true Pandora's box. Every time I had one variable accounted for a couple more popped up to consider.

Your question is a good one ... that I don't know the answer to. If you set up the controller like @stlcharcoal does - where the controller comes on only once in awhile - then the answer is probably they are the same. If you set it up like I do - fan running around 20~30% of the time - then more air cool air is forced into the egg, is heated up to temp, and then vented to the outside. That would suggest that lump usage with the controller is higher ... but, how much?

Maybe not any difference. When the fan is not running, is less air escaping from the egg because the egg is shut down more than it would be when running on solely on natural draft? When using the FB 200 at low temps, my DW holes are closed to a point that would risk the fire going out absent the blower. At high blower percents, I do see the smoke being forced out, but less when running around 20% - 30%.

fishlessman · February 2016

Ragtop99 said:

Jeepster47 said:

fishlessman said:

always wondered how much more gets burned with a controller verse just doing it manually

Got to laugh about that question. I though I had all the variables in hand before taking the first data point. Turned out that lump in an egg is a true Pandora's box. Every time I had one variable accounted for a couple more popped up to consider.

Your question is a good one ... that I don't know the answer to. If you set up the controller like @stlcharcoal does - where the controller comes on only once in awhile - then the answer is probably they are the same. If you set it up like I do - fan running around 20~30% of the time - then more air cool air is forced into the egg, is heated up to temp, and then vented to the outside. That would suggest that lump usage with the controller is higher ... but, how much?

Maybe not any difference. When the fan is not running, is less air escaping from the egg because the egg is shut down more than it would be when running on solely on natural draft? When using the FB 200 at low temps, my DW holes are closed to a point that would risk the fire going out absent the blower. At high blower percents, I do see the smoke being forced out, but less when running around 20% - 30%.

my thoughts would be the controller forces a larger fire feeding and snuffing were my low and slow would start with and maintain a smaller fire. kinda like the guy that steps on the gas only to have to stop t the next light verse the guy that feathers the pedal and times the next light not having to stop

chadpsualum · February 2016

fishlessman said:

Ragtop99 said:

Jeepster47 said:

fishlessman said:

always wondered how much more gets burned with a controller verse just doing it manually

Got to laugh about that question. I though I had all the variables in hand before taking the first data point. Turned out that lump in an egg is a true Pandora's box. Every time I had one variable accounted for a couple more popped up to consider.

Your question is a good one ... that I don't know the answer to. If you set up the controller like @stlcharcoal does - where the controller comes on only once in awhile - then the answer is probably they are the same. If you set it up like I do - fan running around 20~30% of the time - then more air cool air is forced into the egg, is heated up to temp, and then vented to the outside. That would suggest that lump usage with the controller is higher ... but, how much?

Maybe not any difference. When the fan is not running, is less air escaping from the egg because the egg is shut down more than it would be when running on solely on natural draft? When using the FB 200 at low temps, my DW holes are closed to a point that would risk the fire going out absent the blower. At high blower percents, I do see the smoke being forced out, but less when running around 20% - 30%.

my thoughts would be the controller forces a larger fire feeding and snuffing were my low and slow would start with and maintain a smaller fire. kinda like the guy that steps on the gas only to have to stop t the next light verse the guy that feathers the pedal and times the next light not having to stop

What if a big gust of wind came up (in manual) and forced his foot on the gas causing him to accelerate higher than he wanted? Since there was no magic break he could use he'd have to come down naturally.

I see a large, multivariable DOE coming on here. I think BGE should sponsor this research...

Ragtop99 · February 2016

@fishlessman I get the car analogy, but most of the energy difference in that example goes to driver #1 converting his momentum to heat by applying the brakes. There some rotational losses due to differing acceleration rates and maybe peak rpms, but after sitting through heated debates on the use of drivetrain loss percentages to convert rear wheel HP to engine HP, I don't want to go down that path.

NPHuskerFL · February 2016

blind99 · February 2016

Nice work jeepster. My last long cook was roughly 24 hours at 200-250 and it consumed one load of lump, almost to the top of the ring.

Maybe the most useful information from your experiments will be how long can I cook at a given temperature with X lbs of lump.

Now to test other egg sizes...

Toxarch · February 2016

Nice info. It should help give people an idea of how much lump they need for a cook.

lousubcap · February 2016

Once again a great set of data upon which to reasonably understand and apply to your BGE cooks. Your collection of BGE performance data should be compiled and offered as a side-bar file on the main site. Thanks for running and documenting this data. Always a learning eggsperience here.

nolaegghead · February 2016

Scientific method (more or less). You are my hero, man!!!

Jeepster47 · February 2016

nolaegghead said:

Scientific method (more or less). You are my hero, man!!!

@nolaegghead ... you, probably more than most, have a feel for the variables that were glossed over. One could run lump tests for life, but the final conclusion would be the same ... "lump in the bag doesn't help your cook ..."

bloodocean · February 2016

You should probably change your curve fit so that it starts at (0, 0) (because no burn time uses no lump)

Jeepster47 · February 2016

@bloodocean ... the x-axis represents the burn time AT 250 degrees. With that approach the intercept at the y-axis represents the amount of lump used to warm the egg up to 250 degrees and shut it down.

Another way to look at it is to imagine that you start the egg and get it up to 250 degrees. At the instant it reaches 250 degrees you change your mind and shut it down. You will have burned 2/3 of a pound of lump ... which is what the y-axis intercept represents.

Foghorn · February 2016

This is great stuff. Thanks for doing it and posting.

nolaegghead · February 2016

bloodocean said:

You should probably change your curve fit so that it starts at (0, 0) (because no burn time uses no lump)

...so add a y-intercept. More data points are really needed, but this is perfect for a second degree polynomial. What we have now is the classic slope.

Jeepster47 · February 2016

The cool down portion is more amendable to being described by a polynomial equation ... although a sixth order equation was necessary for the greatest accuracy.

Image: https://us.v-cdn.net/5017260/uploads/editor/e8/hgh6fmcreuta.jpg

This data was plotted to see if the "when the fire went out" point would identify itself.

Lump Trivia ... Crusin' at 250

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